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WPF INotifyPropertyChanged双向绑定操作

inotifypropertychanged data-binding mvvm wpf c#

M. Ko · 技术社区 · 5 年前

INotifyPropertyChanged
实施1

public class Notifier : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    public void OnPropertyChanged(string pName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(pName));
    }
}

public class Model : Notifier, IDataErrorInfo
{
    private string name;

    public string Name
    {
        get { return name; }
        set { name = value; OnPropertyChanged("name_changed"); }
    }
}

viewmodel由模型和对模型属性进行更改的命令组成。

public class ViewModel : Notifier
{
    private Model _model;

    public Model Model
    {
        get { return _model; }
        set { _model = value; OnPropertyChanged("model_changed"); }
    }

    private ICommand _cmd;

    public ICommand Command
    {
        get { return _cmd; }
        set { _cmd = value; }
    }

    public void ExecuteCommand(object para)
    {
        Console.WriteLine("Command executed");
        Model.Name = "new name";
    }
}

<TextBox HorizontalAlignment="Center" VerticalAlignment="Center"  Width="100">
    <TextBox.Text>
        <Binding Path="Model.Name" Mode="TwoWay" NotifyOnValidationError="True" UpdateSourceTrigger="PropertyChanged" ValidatesOnDataErrors="True">
            <Binding.ValidationRules>
                <ExceptionValidationRule></ExceptionValidationRule>                
            </Binding.ValidationRules>
        </Binding>
    </TextBox.Text>
</TextBox>

当执行命令时 TextBox
但是,如果我实现 InotifyProperty已更改 喜欢 this

public class Notifier : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected bool SetProperty<T>(ref T field, T newValue, [CallerMemberName]string propertyName = null)
    {
        if (!EqualityComparer<T>.Default.Equals(field, newValue))
        {
            field = newValue;
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
            return true;
        }
        return false;
    }
}

public class Model : Notifier, IDataErrorInfo
{
    private string name;

    public string Name
    {
        get { return name; }
        set { SetProperty(ref name, value); }
    }
}

第一种方法遗漏了什么?

1 回复 | 直到 5 年前

Hemang A 5 年前

请像这样添加属性名。

public class Model : Notifier, IDataErrorInfo
{
    private string name;

    public string Name
    {
        get { return name; }
        set { name = value; OnPropertyChanged("Name"); }
    }
}

Paul Karkoska 5 年前

这是你的字符串参数吗 OnPropertyChanged 方法必须是正在更改的确切属性名。举两个例子, "model_changed" 应改为 "Model" 和 "name_changed" "Name" . 以下是两种很好的技术,可以通过键入文字字符串名称来减轻潜在的人为错误:

CallerMemberName 属性

如果您被允许并有权访问 System.Runtime.CompilerServices 命名空间中,可以这样编写基类,使属性名自动作为方法:

using System.ComponentModel;
using System.Runtime.CompilerServices;

public class Notifier : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    public void OnPropertyChanged([CallerMemberName] string pName = "")
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(pName));
    }
}

OnPropertyChanged() 在你的房子里。

2使用 nameof 关键字

或者,您可以简单地用 nameof(<InsertPropertyNameHere>) 它将返回名称而不存在任何输入错误的风险,例如:

public class Model : Notifier, IDataErrorInfo
{
    private string name;

    public string Name
    {
        get { return name; }
        set { name = value; OnPropertyChanged(nameof(Name)); }
    }
}